These depressions are what makes it a bullaun stone, a type of rock, usually found at early Christian or prehistoric sites across Ireland, featuring one or more cup-shaped indentations whose precise original purpose remains debated. Scholars have variously attributed such hollows to ritual grinding, votive offerings, or simply to the slow work of water on limestone. At this particular stone, the local explanation was rather more vivid.

By 1839, when the Ordnance Survey Letters recorded its name, Glúin Phádraig, meaning Patrick's Knee, the stone had long carried a story told by the local seanchaí, the traditional keeper of oral history. In that account, Finn Mac Cool had made some request of Saint Patrick, which the saint refused. Finn, displeased, took up the rock and hurled it at Patrick's head. It fell short of its target, and Patrick walked over to it, knelt upon it, and pressed the marks of his knees into the stone while praying for protection from so formidable a visitor. The two hollows, in other words, were the physical record of that kneeling. Writing in the 1870s, the scholar Shearman was sceptical, dismissing the marks as mere natural indentations or water-worn features in the limestone, though his dismissal sits alongside his own observation that an old hawthorn bush shaded the stone, its branches hung with strips of cloth left by devotees, the kind of votive offerings, known as ex-vota, that mark a site of active folk devotion rather than simple antiquarian curiosity. Carrigan, writing in 1905, recorded both the stone and the hawthorn, which he called Patrick's Bush, and noted a tradition that a church and graveyard once stood nearby. A standing stone, of the kind referred to in the 1839 letters as a liagan, sits about 300 metres to the north-west.